Senior Health

6/10/2022 | By Terri L. Jones

BMI, or Body Mass Index, has been used by medical professionals for decades to determine if a person’s weight is healthy or not. But BMI may be misleading. Any individual number may overlook other important health factors – fat-to-muscle ratio, weight distribution, race, gender, and age – and give a false sense of security or unnecessary concern.

At some point in your life, you or your doctor has probably calculated your BMI, or Body Mass Index. This measurement factors height and weight to consider your weight status: underweight, healthy, overweight, or obese.

Here’s the quick formula for calculating BMI: weight/height2 x 703. Or better yet, you can use an online calculator like the one provided by the CDC.

If the number you came up with is between 18.5 and 24.9, you might breathe a sigh of relief – that’s rated as “healthy.” However, if it is above or below that range, a medical professional or fitness trainer may advise you to gain or drop a few pounds.

But evaluating your health isn’t that cut and dried, and many experts agree: BMI may be misleading.

The history

First off, the Body Mass Index wasn’t even developed to evaluate an individual’s health … and not by anyone in the medical profession. In the mid-19th century, Belgian mathematician Lambert Adolphe Jacques Quetelet devised the formula to help governments measure the degree of obesity in their populations so they could allocate health and financial resources. While Quetelet himself specifically stated that this measurement was not intended to study the health of individual people, BMI nevertheless has been used for this very purpose for nearly two centuries.

Why BMI may be misleading

diverse group of people - photo by Edhardream, Dreamstime. Feet of person standing on a scale Photo by Vadimgozhda Dreamstime. Body Mass Index or BMI may be misleading, overlooking health factors such as fat-to-muscle ratio, weight distribution, race, gender, and age.

While this measurement can give medical professionals a general idea of their patients’ health, “a too-high or too-low BMI is not an ironclad guarantee that you will develop a chronic disease,” says Dr. Leslie Heinberg, director of Enterprise Weight Management for the Cleveland Clinic. It doesn’t even mean that you’re at an unhealthy weight. That’s because there are so many important factors left out of the equation.

While your weight and height are taken into consideration, BMI does not account for body fat. Or more specifically, it doesn’t differentiate fat from muscle. That means that a very fit, muscular person can have the exact same BMI as someone else with a lot of body fat. Worse yet, because muscle weighs more than fat, the in-shape person could actually have a higher BMI than the soft, sedentary person and be flagged as at risk for disease. Case in point: Tom Brady and The Rock are both considered “overweight” by BMI standards.

The rating also doesn’t factor in your weight distribution. It’s commonly known that a larger waist measurement puts you at higher risk for disease. Explains Heinberg. “Say Person A has a higher waist circumference, carrying their weight in their abdomen. Person B carries their weight lower in their body. Person A has a higher risk of metabolic and cardiovascular disease, but their identical BMI doesn’t tell that story.”

Diverse group of adults socializing outdoors Monkey Business Images Dreamstime. Body Mass Index or BMI may be misleading, overlooking health factors such as fat-to-muscle ratio, weight distribution, race, gender, and age.

Another reason why BMI may be misleading regards variations among ethnic backgrounds. The formula was developed based on a white population and doesn’t account for the varying relationship between weight and disease risk between genders or among various races and ethnicities.

For example, a 2011 study showed that Black women with high BMIs had less metabolic risk than their white counterparts with the same BMIs. And on the opposite side of the spectrum, Asians may have increased risk at lower BMIs, according to the Mayo Clinic. It has to do with how much your fat cells are able to expand before the fat starts being stored in the wrong places, like your liver, and triggering illness.

The age disparity

Research is also showing how age can skew this equation, adding to the reasons that BMI may be misleading. A Body Mass Index on the low end of the range has been shown to potentially lead to health issues for those over the age of 65 and even shorten life expectancy. On the other hand, being overweight or obese at this age has rarely proven to cause earlier death.

Related: A healthy BMI for the over-65 crowd

These findings have resulted in some medical experts, including NIH, recommending that seniors carry a few extra pounds, in the BMI range of 25 to 27. This extra weight may give older people the reserves they need to rebound from stressors like surgery or pneumonia, notes geriatric medicine specialist Thomas Yoshikawa, MD, of UCLA’s David Geffen School of Medicine.

The bottom line

“While BMI is an accessible and affordable way to screen a person’s health, it shouldn’t be relied on as a single measure of health,” says Nicholas Fuller from the University of Sydney.

Your health is like a wheel with many spokes. Since BMI may be misleading, you should consider the whole wheel – from BMI to blood pressure to body shape – to gain an accurate picture of your current health as well as your risk for illness in the future.

Terri L. Jones

Terri L. Jones has been writing educational and informative topics for the senior industry for over 10 years, and is a frequent and longtime contributor to Seniors Guide.

Terri Jones